Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ g Background of the Invention
This invention relates to improvements in heat fusing apparatus and
11 more particularly to heat fusing apparatus in which a heated roll is brought
12 into contact with an image formed of a resinous powder to heat the powder
13 and fix the powder image to a sheet of paper.
14 ~ Contact fusing apparatus is known in the prior art. ~lowever, contact
fusing has the disadvan-tage that "offset" may occur., Offset is caused by
16 part of the image sticking to the surface of the contact fusing device so
17- that when the next sheet comes into contact ~ith the fusing device th~
18 image partially removed from the first sheet is transferred to the second
19 sheet. This offset problem has been overcome in commercial machines by
20 fabricating the outer surface of the heated roll with a resilient material
21 such as silicone rubber which, when operated with a deformable backup roll,
22 will produce offset-free operation without the use of any offsèt-preYenting
23 liquid such as silicone oil. This,fusing rol~l has had sufficient useful
24 life so that it is suitable for use in a system which utilizes high process
speeds .in which the components of the system are required to have maintenance
26 free operation for a long period of time. Ilowever, in actual service,
27 there is a condition where the surface of the heated roll collects toner
28 and paper particles or du~t over a period of operating time which results
29 in thoroughly contaminating tne heated roll's silicone rubber surface
with toner. This condition, which has been known as a "toner ring," causes
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:L mach le mll~unctiorls in the forli o d loss 0, infGrmdtiorl on the pninted
2 sheet causes pa;)er to stick to and wtap aroun(l the ilOt roll alld can cause
3 data insertiorl on the printed page.
1 Sul;ilila~y of tl~ vent on
It is therefore the principle object of -this invention to produce a
fuser appa atus which is capable o-f fusing images without offset at a high
7 process speed which produces maintenance free operation for long periods of
8 time and in which the production of toner rings is inhibited for long
9 periods of time.
It is a further object of -this invention to provide an irnproved method
11 for manufacturing a fuser roll having improved properties.
12 Briefly according to the invention apparatus and a method is provided
13 for manufacturing an improved fuser rol1. The roll is coated with a suitable
14 silicone rubber material and the coatiny is cured. The roll is then treated
by rotating the roll about its axis while simultaneously irradiating its
lG surface with a predetermined level of ultra-violet (UV) radiation for a
17 predetermined time. Although it was known in the art to use UV radiation to
18 fully cure polymèr materials it was unexpec-tedly observed that the post-cure
19 treatrnent ~ith UV according to the invention produced not only greatly im-
20 proved resistance to toner ring formation but also resulted in much lower
21 wear rates.
22 Brief Description of the Drawinac
.
23 FIGURE 1 shows a roll embodiment of the fusing apparatus embodying the
24 present invention;
FIGURE 2 is a schematic view of the apparatus for irradiating the roll
26 surface with ultra-violet radiation.
~7 FIGURE 3 is a plot of fuser roll tack vs. time of exposure to a low
28 pressure UV source; ..
29 FIGURE 4 is a plot-of fuser roll softness vs. time of exposure to a low
pressure UV source;
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1 FlGlJRE 5 is a plot of typical improvelllert in retardation oF fuser
2 ring gro~th vs. time of exposure to a lo~/ pressure UV source;
3 FIG~IRE 6 is d plot of fuser roll tach vs. time of exposure to a
e~ium pressure UV source;
FIGURE 7 is d plot of fuser roll softness vs. time of exposure to a
6 nledil~nl pressure UV source;
7 FIGURE ~ is a plot of typical improvemellt in retardation of fuser
8 ring growth vs. -time of exposure to a medium pressure UV source.
g Description of the Preferred Embodilllent
In the embodinlent shown in Figure l, the fusing apparatus comprises a
11 heated member lO in the shape of a roller which comprises a heat conducting
12 base member 12 having infra-red lamps 14 disposed therein and having a
13 deformable layer 16 of an insulating high temperature material such as one
comprising silicone rubber on its outer surface. The power to the lamps l4
will vary depending upon the speed of the paper web 24 through the fusing
16 station and the desired temperature for the hot roll surface temperature.
17 The base melllber comprises a tube l2 made from a suitable material such as
18 copper or aluminum which is a good heat conductor. However, since high
19 temperature materials such as silicone rubber are heat insulating materials,
the thickness of the deformable layer 16 must be kept thin and, in a prac-
21 tical embodiment, this thickness would norrnally be ten mils or less. The
22 backup element l8 is also in the r1ape of a roller, and the roller is
23 pushed against the heated roll with a meshing force supplied in the illus-
2~ trated embodiment by cam means 20. The backup element is also formed of a
25 high temperature elastomer 22 such as one comprising silicone rubber.
26 Heated roll lO is driven by a suitable rnotor and when backup roll l3
27 is meshed with the heated roll, the pressure causes paper web 24 to be
2~ driven through the hot roll fuser and to l~use and permanently fix the toner
29 image to sheet 24. Paper web 24 rmay comprise roll paper, separate sheets
of paper or fan-fold paper sheets. The fan-fold paper sheets produce
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I yreater wear on the deformable layer due to the presence of the tractor ~
2 holes in the fan-Fold paper.
3 Accordillg to the present invention, an improved method for manufacturing
~1 a fuser roll comprising tube 12 and deformable layer 16 is disclosed which
__~ 5 has a greatly increased useful life. The fuser roll should have the properties
at temperatures suitable for -fusing toner, of release from the toner aFter
7 fusing, wear resistance to fan-fold paper especially at tractor holes,
8 acceptable heat transfer and ability to elastically deform under load to
g give contact with toner during Fusing. The time during which the fuser
roll retains these properties is its useful life.
11 These properties can be obtained according -to our invention by forming
12 de-Formable layer 16 with a suitable silicone rubber material. The silicone
13 rubber material is then cured by~any one of several suitable curing methods
1~ known in the art. One suitable curing method is described and claimed in
U.S. patent 3,987,530 to Atkin et al which patent is assigned to the assignee
16 of the present invention. In this curing method, the base member is coated
17 with a silicone gum material containing no curing agent, and then treated
18 by heating in an inert abllosphere to a temperature at which substantial
19 cross-linking occurs for a predetermined time to produce a tough long-
wearing silicone rubber deformable layer.
21 The cured silicone rubber deformable layer 16 on tube 12 is then
22 subjected to a treating step whic;l comprises exposing the roll to a predeter-
23 mined level of ultra-violet radiation for a predetermined time. The level
2a~ of ultra-violet radiation and the time oF exposure is determined by consider-
ing not only the effect of the radiation in the forma-tion of toner rings,
26 but also the efFec-t on other characteristics of the roll which define the
27 useful life of the roll. Figures 3, 4 and 5 relate to rolls treated with a
2~3 low-level ultra-violet radiation. Thin .ections of silicone rubber tend to
29 have a tacky surface even when Fully cured, by all the conventional tests,
such as modulus of elasticity, tensile strength, elongation and cross-link
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I density. Figure 3 gives ~he relation of the measured tack of -the roll with
2 various treatment times with the low level UV. Tack is a measure of the
3 stickiness of the roll and is measured by placiny a standard size sheet
~ in contac-t with the roll and measuring the force in grallls required to peel
the sheet off the roll. The tack goes to zero by about a six hour exposure
6 for the low level UV exposure.
7 The softness of a roll is defined as the ratio of the indentation of a
8 standard probe to the -total thickness of the silicone rubber coating. Figure
9 4 shows the relation of softness of the roll of Figure 3 to time of exposure.
It can be noted from Figure 4 that the softness decreases (i.e., roll becomes
11 harder) with increased exposure. It can be seen that the softness remains
12 above 50,' until about 9 hours of treatment. Figure 5 shows the improvement
13 in number o-f copies produced before onset of toner rlngs for different times
~ of exposure to the low level UV radiation. Figures 3, ~ and 5 show that a
15 treatment time of about 6 hours appears to be optimum.
16 Figures 6, 7 and 8 show the results of treatnlellt with a mediunl pressure
17 mercury arc lamp. The treatment times are much less than with the low pres-
18 sure radiation as can be seen by the tack curve in Figure 6 in which the tack
19 goes substantially to zero after about 6 minutes treatment. However, the
2~ softness is decreased more rapidly with this treatment. It can be seen that
21 the optimum time for this level of UV radiation is a few minutes, although the
22 improvement in performance is not as great as was the case with the low level
23 eXpOSure.
24 The low level exposure is the preferred treatment due to the level of
25 improvement achieved. However, in some cases a lower level of improvement
26 may be adequate in view of the difference in processing time.
27 The apparatus for providing the -treating step is shown in Figure 2.
28 The roll lO is placed in a suitable fixture (not shown) so that the roll lO
29 can be continuously rotated about its axis as shown by the arrow in the
30 drawing to provide relative motion be-tween the radiation source and the
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1 peripheral surface of the roll. The rotation is preferably at a low speed
2 and.is not critical. In some cases it may be advantageous to provide the
3 relative motion by moving the radiation source. As the roll is rotating
I its ou~er peripheral surface is irradiated with a low level ultra-violet
radiation provided by a suitable source such as a mercury arc lamp 30. A
reflector 32 is preferably provided to direct the radiation toward the roll
7 lO. The surface of the roll lO is ~ept in an inert atmosphere during the
8 treating step under some conditions. The inert atmosphere is provided since
9 the UV radiation in the presence of oxygen may produce ozone which poisons
the silicone rubber coating. In the examples previously discussed the low
11 level radiation treatment requires the inert atmosphere during treatment
12 but the mediunl pressure UV treatnlent does not require the inert atmosphere
13 during treatment. The reason that the inert atmosphere is not required for
14 the mediunl pressure treatment is either that the spectral output of the
medium pressure lan~ps used does not generate ozone or that the heat generated
16 by the lamp breaks down the ozone as quickly as i~ is formed. A cylindrical
17 member 34 is mounted in a fixed position surrounding the roll to confine
18 the inert atmosphere. Cylindrical member 34 is macle from a suitable material
19 that is t~ansparent to the ultra-violet radiation. The preferred material
is a quartz tube. The inert atmosphere is provided by filling the area
21 between roll lO and the inner pe~- nheral surface of cylindrical tube melllber
22 34 with a suitable inert atmosptle;e. The preferred inert atmosphere is
23 nitrogen and the nitrogen is present in sufficient quantity to provide a
2~ flow of about ten cubic feet per hour in the area between the heated roll
and tile tube 34. The low level ultra-violet radiation is produced for a
2G predetermined time at a low level. For a specific roll and using a Pen Ray *
27 lalllp number 3SC-9 and a General Electric type 20~ quartz tube the preferred
28 exposure is four milliwat~s per centimeter squared when measured at the 254
29 nanometer line o~ tlle spectrum from the lamp 30 and this level of radiation
is produced for an exposure time of six hours ~/itil the roll lO rotating
31 * Registered ~rade Mark
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1 about its ax-is at a speed of approxilllately 50 RPM. This level of exposure
2 and.timiny produces a -fuser roll which not only inhibits the formation of
3 toner rings for a substantial time as sho~Jn in Figure 5, but also produces
4 about one-third lower wear rate.
The reasons for this improved performance due to the described treatment
6 is not fully understood, bu-t lowering the tack of the rolls appears to con-
7 tribute to the results. One -theory for the improved performance is that
8 the prior art rolls were not Fully cured, and this is the reason that the
9 paper sizing material, the paper dust and the toner finally combined to
procluce the toner rings. However, this does not appear to be the correc-t
11 theory since the silicone rubber coating of the prior art rolls was fully
2 cured by all the conventional tests, such as modulus of elasticity, tensile
13 strength, elongation and cross-link density. In-addition, the problem seems
14 to be present wi-th all curing me-thods.
Another theory is that -for some unknown reason the silicone rubber
6 coating on the prior art rolls was not cured well on the surface. However,
17 this also does not appear to be the proper explana-tion since the heated
18 roll starts out with a coating of silicone rubber about lO mils thick. This
19 thickness is reduced by abrasive wear during use and will a roll prepared
according to the present invention, the beneficial effect is still apparent
21 with a few mils wear on the roll. This indicates that the explanation is
22 not a surface phenomena since no ~urface phenomena would be present a sub- -
23 stantial depth into the coating. !
2a~ llhile the invention has been particularly shown and described with
reference to a preferred embodiment thereof, it will be und-erstood by those
26 skilled in the art that various changes in the form and de-tails may be made
27 therein without departing from the spirit and scope o-f the inven-tion.
28
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